On the file /etc/postfix/main.cf complete the above line: virtual_alias_maps = ..., ldap:institutionalAccounts And include block too: # Institutional Accounts institutionalAccounts_server_host = ldap://ldap.foo.com institutionalAccounts_version = 3 institutionalAccounts_timeout = 10 institutionalAccounts_chase_referral = 0 institutionalAccounts_search_base = institutionalAccounts_query_filter = (&(mail=%s)(phpgwAccountType=i)(objectClass=phpgwAccount)(accountStatus=active)) institutionalAccounts_domain = hash:/etc/postfix/expresso-dominios institutionalAccounts_result_attribute = mailForwardingAddress institutionalAccounts_bind = no